The performance objectives of disposable absorbent articles, such as infant diapers, include leakage prevention, dry feel to the wearer, and a comfortable fit throughout the product life. Accordingly, absorbent articles have typically contained an absorbent core to provide liquid handling and other absorbent functionalities required to meet the product performance objectives. The absorbent core of a conventional absorbent article has typically been composed of absorbent fibers, and a superabsorbent material has typically been combined with the absorbent fibers to increase the liquid absorbent capacity. The absorbent core has been formed in a substantially rectangular shape. The absorbent core has also been formed in an hourglass shape, a I-shape, a T-shape, or similar configuration with a reduced absorbent width in the central crotch region for improved fit and comfort.
Conventional absorbent cores have incorporated dry-formed materials which have been produced with various conventional airlaying techniques. The airlaying techniques have typically laid an air-directed mixture of absorbent fibers and superabsorbent to form a web of the absorbent material. When dry, the conventional dry-formed absorbent structures have been soft and conformable, but have had low strength. In addition, the dry-formed structures have had low integrity after they have been wetted.
Conventional absorbent cores have also incorporated wet-formed materials which have been produced with various wet-laying techniques. The wet-laying techniques have typically formed an absorbent web produced from a precursor material composed of a mixture of fibers and superabsorbent particles combined with water or other aqueous liquid. A particular wet-laying technique has processed the precursor material into a foam, and the foam has then been employed to form the desired web of absorbent material. The absorbent structures produced from wet-formed absorbent materials have had greater strength and greater integrity. In particular, the wet-formed absorbent structures have exhibited greater strength and greater integrity after the absorbent materials have absorbed liquid. The wet-formed absorbent materials, however, have also had excessive stiffness and rigidity, particularly when the absorbent materials have been provided at the basis weights and amounts needed to provide desired levels of total absorbent capacity.
Particular methods for reducing the stiffness of absorbent web materials have included a passing of the material through the nip of a pair of counter-rotating compression rollers. Other methods have embossed the webs to impart increased flexibility. Still other methods have included a passing of the material through the nip of a pair of counter-rotating rollers having textured outer surfaces. The textured surfaces have been configured to produce localized stresses and localized strains which have helped to reduce the rigidity of the material. Where the webs contain superabsorbent particles, the compression rollers have been configured to fracture or crush the superabsorbent materials.
Conventional techniques, such as those mentioned above, have not been adequate for softening or compressing webs which contain superabsorbent materials. The conventional techniques have caused excessive fracturing of the superabsorbents and have increased the relative proportions of smaller superabsorbent particles in the webs. This change in the size distributions of the superabsorbent particles has adversely affected the absorbent properties of the web, has increased the tendency of the superabsorbent to shake-out of the web, and has allowed the generation of excessive dust. In addition, the fracturing of the superabsorbent material has adversely affected various absorbent properties, such as the intake rate of the superabsorbent and the ability of the superabsorbent to swell under pressure.
As a result, there remains a need for improved methods for compressing or otherwise processing stiff absorbent materials to improve the strength, softness, flexibility, wet integrity and absorbent capacity of the materials.